adv_agentx.py

# python-agentx module
#
#  Copyright (C) 2010 Bozhin Zafirov, bozhin@abv.bg
#
#  This program is free software: you can redistribute it and/or modify
#  it under the terms of the GNU General Public License as published by
#  the Free Software Foundation, either version 3 of the License, or
#  (at your option) any later version.
#
#  This program is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#  GNU General Public License for more details.
#
#  You should have received a copy of the GNU General Public License
#  along with this program.  If not, see <http://www.gnu.org/licenses/>.
#

#
#  some adaption for SnmpGauge32/SnmpCounter32/SnmpIpAddress support:
#  by Tobias Hintze <tobias.hintze@travelping.com>
#  Copyright (c) 2016 Travelping GmbH <copyright@travelping.com>
#  (The original was imported from http://python-agentx.sf.net at r8)
#


from builtins import map
from builtins import object
import ctypes
import ctypes.util
import time
import signal
import os
import sys
import socket  # for inet_aton
import locale

# export names
__all__ = [
    'AgentX',
]

# snmp agentx library
snmp = None
axl = None
try:
    snmp = ctypes.cdll.LoadLibrary(ctypes.util.find_library('netsnmphelpers'))
    axl = ctypes.cdll.LoadLibrary(ctypes.util.find_library('netsnmpagent'))
except BaseException:
    print('ERROR: agentx module requires net-snmp libraries, terminating...')
    sys.exit(1)

# constants
NETSNMP_DS_APPLICATION_ID = 1
NETSNMP_DS_AGENT_ROLE = 1

# ASN constants
ASN_BOOLEAN = 0x01
ASN_INTEGER = 0x02
ASN_BIT_STR = 0x03
ASN_OCTET_STR = 0x04
ASN_NULL = 0x05
ASN_OBJECT_ID = 0x06
ASN_SEQUENCE = 0x10
ASN_SET = 0x11

ASN_UNIVERSAL = 0x00
ASN_APPLICATION = 0x40
ASN_CONTEXT = 0x80
ASN_PRIVATE = 0xC0

ASN_PRIMITIVE = 0x00
ASN_CONSTRUCTOR = 0x20

ASN_LONG_LEN = 0x80
ASN_EXTENSION_ID = 0x1F
ASN_BIT8 = 0x80

ASN_IPADDRESS = ASN_APPLICATION | 0x0
ASN_COUNTER32 = ASN_APPLICATION | 0x1
ASN_UNSIGNED = ASN_APPLICATION | 0x2
ASN_TIMETICKS = ASN_APPLICATION | 0x3
ASN_APP_FLOAT = ASN_APPLICATION | 0x8
ASN_APP_DOUBLE = ASN_APPLICATION | 0x9


# python lacks some primitive types to represent
# some snmp types. define some wrapper types:
class SnmpGauge32(int):
    pass


class SnmpCounter32(int):
    pass


class SnmpIpAddress(str):
    pass


# asn opaque
ASN_OPAQUE_TAG2 = 0x30
ASN_OPAQUE_FLOAT = ASN_OPAQUE_TAG2 + ASN_APP_FLOAT
ASN_OPAQUE_DOUBLE = ASN_OPAQUE_TAG2 + ASN_APP_DOUBLE

# handler constants
HANDLER_CAN_GETANDGETNEXT = 0x01
HANDLER_CAN_SET = 0x02
HANDLER_CAN_GETBULK = 0x04
HANDLER_CAN_NOT_CREATE = 0x08
HANDLER_CAN_BABY_STEP = 0x10
HANDLER_CAN_STASH = 0x20

HANDLER_CAN_RONLY = HANDLER_CAN_GETANDGETNEXT
HANDLER_CAN_RWRITE = HANDLER_CAN_GETANDGETNEXT | HANDLER_CAN_SET
HANDLER_CAN_SET_ONLY = HANDLER_CAN_SET | HANDLER_CAN_NOT_CREATE
HANDLER_CAN_DEFAULT = HANDLER_CAN_RONLY | HANDLER_CAN_NOT_CREATE

SNMP_ERR_NOERROR = 0
SNMP_ERR_TOOBIG = 1
SNMP_ERR_NOSUCHNAME = 2
SNMP_ERR_BADVALUE = 3
SNMP_ERR_READONLY = 4
SNMP_ERR_GENERR = 5

ASN_CONSTRUCTOR = 0x20

SNMP_MSG_GET = ASN_CONTEXT | ASN_CONSTRUCTOR | 0x0
SNMP_MSG_GETNEXT = ASN_CONTEXT | ASN_CONSTRUCTOR | 0x1
SNMP_MSG_RESPONSE = ASN_CONTEXT | ASN_CONSTRUCTOR | 0x2
SNMP_MSG_SET = ASN_CONTEXT | ASN_CONSTRUCTOR | 0x3
SNMP_MSG_TRAP = ASN_CONTEXT | ASN_CONSTRUCTOR | 0x4
SNMP_MSG_GETBULK = ASN_CONTEXT | ASN_CONSTRUCTOR | 0x5
SNMP_MSG_INFORM = ASN_CONTEXT | ASN_CONSTRUCTOR | 0x6
SNMP_MSG_TRAP2 = ASN_CONTEXT | ASN_CONSTRUCTOR | 0x7

SNMP_MSG_INTERNAL_SET_BEGIN = -1
SNMP_MSG_INTERNAL_SET_RESERVE1 = 0
SNMP_MSG_INTERNAL_SET_RESERVE2 = 1
SNMP_MSG_INTERNAL_SET_ACTION = 2
SNMP_MSG_INTERNAL_SET_COMMIT = 3
SNMP_MSG_INTERNAL_SET_FREE = 4
SNMP_MSG_INTERNAL_SET_UNDO = 5
SNMP_MSG_INTERNAL_SET_MAX = 6


MAX_OID_LEN = 128
OID_LEN = MAX_OID_LEN * 2 + 1

# --- agentx.py constants ---
PAX_RO = 0x0
PAX_WO = 0x1
PAX_RW = 0x2

# --- low level routines ---


# types
# oid type definition
oid_t = ctypes.c_ulong
oidOID_t = oid_t * MAX_OID_LEN
strOID_t = ctypes.c_char * OID_LEN


# structures

# dummy structures (pointers only)
class netsnmp_mib_handler(ctypes.Structure):
    pass


class netsnmp_handler_registration(ctypes.Structure):
    pass


class netsnmp_subtree(ctypes.Structure):
    pass


class netsnmp_agent_session(ctypes.Structure):
    pass


class counter64(ctypes.Structure):
    pass


class netsnmp_vardata(ctypes.Union):
    _fields_ = [
        ('integer', ctypes.POINTER(ctypes.c_long)),
        ('string', ctypes.c_char_p),
        ('objid', ctypes.POINTER(oid_t)),
        ('bitstring', ctypes.POINTER(ctypes.c_ubyte)),
        ('counter64', ctypes.POINTER(counter64)),
        ('floatVal', ctypes.POINTER(ctypes.c_float)),
        ('doubleVal', ctypes.POINTER(ctypes.c_double)),
    ]


class netsnmp_variable_list(ctypes.Structure):
    pass


netsnmp_variable_list._fields_ = [
    ('next_variable', ctypes.POINTER(netsnmp_variable_list)),
    ('name', ctypes.POINTER(oid_t)),
    ('name_length', ctypes.c_size_t),
    ('type', ctypes.c_ubyte),
    ('val', netsnmp_vardata),
    ('val_len', ctypes.c_size_t),
    ('name_loc', oid_t * MAX_OID_LEN),
    ('buf', ctypes.c_ubyte * 40),
    ('data', ctypes.c_void_p),
    ('dataFreeHook', ctypes.c_void_p),
    ('index', ctypes.c_int),
]
netsnmp_variable_list_p = ctypes.POINTER(netsnmp_variable_list)


class netsnmp_data_list(ctypes.Structure):
    pass


netsnmp_data_list._fields_ = [
    ('next', ctypes.POINTER(netsnmp_data_list)),
    ('name', ctypes.c_char_p),
    ('data', ctypes.c_void_p),
    ('free_func', ctypes.c_void_p),
]


class netsnmp_agent_request_info(ctypes.Structure):
    _fields_ = [
        ('mode', ctypes.c_int),
        ('asp', ctypes.POINTER(netsnmp_agent_session)),
        ('agent_data', ctypes.POINTER(netsnmp_data_list)),
    ]


class netsnmp_request_info(ctypes.Structure):
    pass


netsnmp_request_info._fields_ = [
    ('requestvb', ctypes.POINTER(netsnmp_variable_list)),
    ('parent_data', ctypes.POINTER(netsnmp_data_list)),
    ('agent_req_info', ctypes.POINTER(netsnmp_agent_request_info)),
    ('range_end', ctypes.POINTER(oid_t)),
    ('range_end_len', ctypes.c_size_t),
    ('delegated', ctypes.c_int),
    ('processed', ctypes.c_int),
    ('inclusive', ctypes.c_int),
    ('status', ctypes.c_int),
    ('index', ctypes.c_int),
    ('repeat', ctypes.c_int),
    ('orig_repeat', ctypes.c_int),
    ('requestvb_start', ctypes.POINTER(netsnmp_variable_list)),
    ('next', ctypes.POINTER(netsnmp_request_info)),
    ('prev', ctypes.POINTER(netsnmp_request_info)),
    ('subtree', ctypes.POINTER(netsnmp_subtree)),
]


# various functions argument types
axl.read_objid.argtypes = [
    ctypes.c_char_p,
    ctypes.POINTER(oidOID_t),
    ctypes.POINTER(
        ctypes.c_size_t)]
axl.snmp_set_var_typed_value.argtypes = [
    ctypes.POINTER(netsnmp_variable_list),
    ctypes.c_ubyte,
    ctypes.POINTER(
        ctypes.c_ubyte),
    ctypes.c_int]
axl.snprint_objid.argtypes = [
    strOID_t,
    ctypes.c_int,
    ctypes.POINTER(oid_t),
    ctypes.c_int]
axl.snmp_varlist_add_variable.argtypes = [
    ctypes.POINTER(netsnmp_variable_list_p),
    ctypes.POINTER(oid_t),
    ctypes.c_long,
    ctypes.c_ubyte,
    ctypes.c_char_p,
    ctypes.c_long]
axl.send_v2trap.argtypes = [netsnmp_variable_list_p]

# convert text oid to oid list


def ReadOID(TextOID):
    oidOID = oidOID_t()
    oidOID_len = ctypes.c_size_t(MAX_OID_LEN)
    if axl.read_objid(
            TextOID.encode('utf-8'),
            ctypes.byref(oidOID),
            ctypes.byref(oidOID_len)) == 0:
        raise OperationalError('Incorrect OID (%(oid)s)' % {'oid': TextOID})
    newOID_t = oid_t * oidOID_len.value
    oid = newOID_t(*oidOID[0:oidOID_len.value])
    return oid

# convert to text oid


def ReadTOID(oid):
    strOID = strOID_t()
    oid_list = list(map(int, oid.split('.')))
    oid = (oid_t * len(oid_list))(*oid_list)
    axl.snprint_objid(strOID, OID_LEN, oid, len(oid))
    return strOID.value

def b(s):
    """ Encodes Unicode strings to byte strings, if necessary. """
    return s if isinstance(s, bytes) else s.encode(locale.getpreferredencoding())

# exceptions


class OperationalError(Exception):
    pass


# agentx data object
class AgentXData(dict):
    def __init__(self):
        dict.__init__(self)
        self.ResponseLast = None
        self.container = None

    # clear data
    def Clear(self):
        self.clear()
        self.ResponseLast = None

    # register variable
    def RegisterVar(self, oid, value=None):
        # normalize
        oid = self.NormOID(oid)
        if self:
            self[self.ResponseLast]['noid'] = oid
        self.ResponseLast = oid
        self[oid] = {'value': value, 'noid': None}

    # prepare snmp table data
    def Table(self, entry, columns):
        self.RegisterVar('%(TableEntry)s.0' % {'TableEntry': entry}, 0)
        for column in columns:
            i = 1
            for value in columns[column]:
                self.RegisterVar('%(ColumnName)s.%(RowId)d' %
                                 {'ColumnName': column, 'RowId': i}, value)
                i += 1

    # get next object id
    def GetNext(self, oid):
        return self[oid]['noid']

    # set value
    def Update(self, oid, value):
        if oid not in self:
            raise OperationalError(
                'No such object registered: %(oid)s' % {
                    'oid': oid})
        self[oid]["value"] = value

    # normalize text id
    def NormOID(self, tid):
        if tid.find('::') == -1:
            if not self.container:
                raise OperationalError(
                    'OID prefix is not yet available, run ax.Init first.')
            tid = '%(mib)s::%(oid)s' % {'mib': self.container, 'oid': tid}
        return tid


# forward declaration
AXObject = None

# snmp agentx request object


class RequestObject(object):
    __slots__ = [
        'oid',
        'mode',
        'value',
        'data',
        '__ax',
        '__request',
        '__reqinfo']
    # class constructor

    def __init__(self, ax, request, reqinfo):
        self.__ax = ax
        self.__request = request
        self.__reqinfo = reqinfo

    # set next object id
    def SetNext(self, objid):
        oidOID = ReadOID(objid)
        axl.snmp_set_var_objid(self.__request.requestvb, oidOID, len(oidOID))
        self.oid = objid

    # get next objid
    def GetNext(self, oid=None):
        if not oid:
            oid = self.oid
        return self.__ax.AXData.GetNext(oid)

    # set value
    def SetValue(self, value):
        # set object type
        otype = None
        size = 8
        if isinstance(value, str):
            otype = ASN_OCTET_STR
            size = len(value)
            value = value.encode('utf-8')
            value = ctypes.c_char_p(value)
        elif isinstance(value, int):
            otype = ASN_INTEGER
            value = ctypes.pointer(ctypes.c_int(value))
        elif isinstance(value, float):
            otype = ASN_APP_FLOAT
            value = ctypes.pointer(ctypes.c_float(value))
        elif isinstance(value, SnmpIpAddress):
            otype = ASN_IPADDRESS
            size = 4
            value = ctypes.c_char_p(socket.inet_aton(value))
        elif isinstance(value, SnmpCounter32):
            otype = ASN_COUNTER32
            value = ctypes.pointer(ctypes.c_uint(value))
        elif isinstance(value, SnmpGauge32):
            otype = ASN_UNSIGNED
            value = ctypes.pointer(ctypes.c_uint(value))
        try:
            axl.snmp_set_var_typed_value(self.__request.requestvb, otype, ctypes.cast(
                value, ctypes.POINTER(ctypes.c_ubyte)), size)
            self.value = value
        except Exception as e:
            print("WARNING: Unexpected error in SetValue(): %r" % e)

    # set error
    def SetError(self, error):
        axl.netsnmp_set_request_error(self.__reqinfo, self.__request, error)


# callback function
HandlerWrapperFunc = ctypes.CFUNCTYPE(
    ctypes.c_int,
    ctypes.POINTER(netsnmp_mib_handler),
    ctypes.POINTER(netsnmp_handler_registration),
    ctypes.POINTER(netsnmp_agent_request_info),
    ctypes.POINTER(netsnmp_request_info)
)
# high level handler


def _handler_wrapper(handler, reginfo, reqinfo, requests):
    r = requests.contents
    # get current time
    timestamp = time.time()
    if AXObject.CacheInterval and timestamp - \
            AXObject.UpdateTime > AXObject.CacheInterval:
        # need to update data now
        AXObject.AXData.Clear()
        AXObject.GlobalsRun('OnUpdate')
        AXObject.UpdateTime = timestamp
    # handler loop
    while True:
        # get object id
        strOID = strOID_t()
        axl.snprint_objid(
            strOID,
            OID_LEN,
            r.requestvb.contents.name,
            r.requestvb.contents.name_length)

        # do some magic here
        req = RequestObject(AXObject, r, reqinfo)
        req.oid = strOID.value
        # python 3.x stores oid in bytes object
        if not isinstance(req.oid, str):
            req.oid = req.oid.decode()
        req.mode = reqinfo.contents.mode

        if req.mode == SNMP_MSG_GET:
            if req.oid in AXObject.AXData:
                req.SetValue(AXObject.AXData[req.oid]['value'])
                # run read-write and read-only handlers
                for handler in AXObject.RequestHandlers[PAX_RW] + \
                        AXObject.RequestHandlers[PAX_RO]:
                    value = handler(req, AXObject, AXObject.AXData)
                    if value:
                        req.SetValue(value)
        elif req.mode == SNMP_MSG_GETNEXT:
            if req.oid in AXObject.AXData:
                if AXObject.AXData[req.oid]['noid'] is None:
                    # only set current objid
                    req.SetNext(req.oid)
                else:
                    # req.SetNext changes req.oid value
                    req.SetNext(AXObject.AXData[req.oid]['noid'])
                    req.SetValue(AXObject.AXData[req.oid]['value'])
                    # run read-write and read-only handlers
                    for handler in AXObject.RequestHandlers[PAX_RW] + \
                            AXObject.RequestHandlers[PAX_RO]:
                        value = handler(req, AXObject, AXObject.AXData)
                        if value:
                            req.SetValue(value)
        elif req.mode == SNMP_MSG_INTERNAL_SET_COMMIT:
            # FIXME: MAX-ACCESS is now ignored :(
            if r.requestvb.contents.type in (ASN_INTEGER, ASN_UNSIGNED):
                req.value = r.requestvb.contents.val.integer.contents.value
            elif r.requestvb.contents.type == ASN_OCTET_STR:
                req.value = r.requestvb.contents.val.string
            elif r.requestvb.contents.type in (ASN_OPAQUE_FLOAT, ASN_OPAQUE_DOUBLE):
                req.value = r.requestvb.contents.val.floatVal.contents.value
            # check special case oids
            if AXObject.ReloadOID and AXObject.ReloadOID == req.oid and req.value == 1:
                # reload requested by snmp
                AXObject.GlobalsRun('OnReload')
            if AXObject.StopOID and AXObject.StopOID == req.oid and req.value == 1:
                # stop agent
                AXObject.Shutdown()
            # run read-write and write-only handlers
            for handler in AXObject.RequestHandlers[PAX_RW] + \
                    AXObject.RequestHandlers[PAX_WO]:
                value = handler(req, AXObject, AXObject.AXData)
                if value:
                    req.value = value
            # save value
            try:
                AXObject.AXData.Update(req.oid, req.value)
            except OperationalError:
                AXObject.AXData.RegisterVar(req.oid, req.value)
        if not r.next:
            break
        r = r.next.contents
    return SNMP_ERR_NOERROR


# low level handler
handler_wrapper = HandlerWrapperFunc(_handler_wrapper)


# AgentX object declaration
class AgentX(object):
    def __init__(self, Globals, **args):
        self.alarm = 0
        self.loop = False
        self.AXData = AgentXData()
        self.Globals = Globals
        self.UpdateTime = 0

        # save global constants in object's namespace
        for c in globals():
            for prefix in ('ASN_', 'SNMP_', 'HANDLER_', 'PAX_'):
                if c.startswith(prefix):
                    setattr(self, c, globals()[c])
                    break

        # default settings
        defaults = {
            'Name': os.path.splitext(os.path.basename(sys.argv[0]))[0],
            'CacheInterval': 30,
            'TimerInterval': 30,
            'Master': False,
            'MIBFile': (),
            'RootOID': None,
            'ReloadOID': None,
            'StopOID': None,
        }

        # initialize variables
        for key in defaults:
            setattr(self, key, args.get(key, defaults[key]))

        # request handlers
        self.RequestHandlers = {
            PAX_RO: [],
            PAX_WO: [],
            PAX_RW: [],
        }

        # set global object reference
        global AXObject
        AXObject = self

        # initialize agentx
        # setup log facility
        axl.snmp_enable_stderrlog()
        if not self.Master:
            axl.netsnmp_ds_set_boolean(
                NETSNMP_DS_APPLICATION_ID, NETSNMP_DS_AGENT_ROLE, 1)
        # init agent module
        # for win32: winsock_startup()
        axl.init_agent(self.Name)
        axl.init_snmp(self.Name)
        # register agent
        if not type(self.MIBFile) in (list, tuple):
            self.MIBFile = (self.MIBFile,)
        for mib in self.MIBFile:
            axl.read_mib(b(mib))

        # install low level handler
        if self.RootOID:
            self.AXData.container = self.RootOID.split('::', 1)[0]
            # register handler callback
            oidOID = ReadOID(self.RootOID)

            axl.netsnmp_create_handler_registration.restype = ctypes.POINTER(
                netsnmp_handler_registration)
            h = axl.netsnmp_create_handler_registration(
                self.Name,
                handler_wrapper,
                oidOID, len(oidOID),
                HANDLER_CAN_RWRITE,
            )
            if axl.netsnmp_register_handler(h) != 0:
                raise OperationalError('SNMP handler registration failure.')
        # register custom handlers
        for HandlerName, HandlerMode in (
                ('OnSnmpRequest', PAX_RW), ('OnSnmpRead', PAX_RO), ('OnSnmpWrite', PAX_WO)):
            if HandlerName in self.Globals and '__call__' in dir(
                    self.Globals[HandlerName]):
                self.RegisterHandler(self.Globals[HandlerName], HandlerMode)
        # ReloadOID and StopOID
        if self.ReloadOID:
            self.ReloadOID = self.AXData.NormOID(self.ReloadOID)
        if self.StopOID:
            self.StopOID = self.AXData.NormOID(self.StopOID)

        # attach HUP signal
        def HupHandler(signum, frame):
            # reload requested by HUP signal
            self.GlobalsRun('OnReload')
        signal.signal(signal.SIGHUP, HupHandler)

        # run custom init routine
        self.GlobalsRun('OnInit')
        if not self.loop:
            # start timer
            self.TimerStart(self.TimerInterval)
            self.loop = True
            while self.loop:
                self.GlobalsRun('OnTimer')
                self.Process()

    # register custom handler
    def RegisterHandler(self, handler, mode=PAX_RW):
        assert '__call__' in dir(handler), 'Callable object is required'
        self.RequestHandlers[mode].append(handler)

    # start itimer
    def TimerStart(self, interval):
        try:
            signal.setitimer(signal.ITIMER_REAL, interval, interval)
        except BaseException:
            # fallback to alarm clock which is more inacurate
            self.alarm = int(interval)
            if not self.alarm:
                self.alarm = 1
            return self.alarm
        return interval

    # stop alarm timer
    def TimerStop(self):
        try:
            signal.setitimer(signal.ITIMER_REAL, 0)
        except BaseException:
            self.alarm = 0

    # process snmp requests
    def Process(self, block=True):
        alarm_triggered = False
        loop = True
        result = True

        if self.alarm:
            # start alarm
            signal.alarm(self.alarm)
            block = True

        # alarm handler
        def sigalrm_handler(signum, frame):
            alarm_triggered = True

        # attach alarm signal handler
        signal.signal(signal.SIGALRM, sigalrm_handler)

        # process loop
        while loop and self.loop:
            r = axl.agent_check_and_process(block)
            if r == -1:
                if not alarm_triggered:
                    result = False
                loop = False
            elif r == 0 and not block:
                loop = False

        # detach alarm signal
        signal.signal(signal.SIGALRM, signal.SIG_DFL)
        # stop alarm timer
        if self.alarm:
            signal.alarm(0)
        return result

    # run globals routine
    def GlobalsRun(self, name, *args):
        if name in self.Globals and '__call__' in dir(self.Globals[name]):
            # call
            if args:
                self.Globals[name](self, self.AXData, *args)
            else:
                self.Globals[name](self, self.AXData)

    # end main loop
    def Shutdown(self):
        self.loop = False

    # send trap from within agentx module
    def Trap(self, oid, *args):
        sysUpTimeOID = (oid_t * 9)(1, 3, 6, 1, 2, 1,
                                   1, 3, 0)		# sysUpTimeInstance
        snmpTrapOID = (oid_t * 11)(1, 3, 6, 1, 6, 3,
                                   1, 1, 4, 1, 0)  # snmpTrapOID.0
        TrapOID = ReadOID(self.AXData.NormOID(oid))

        TrapVars = netsnmp_variable_list_p()
        uptime = ctypes.c_long(axl.netsnmp_get_agent_uptime())

        # agent uptime
        axl.snmp_varlist_add_variable(
            ctypes.byref(TrapVars),
            ctypes.cast(
                ctypes.byref(sysUpTimeOID),
                ctypes.POINTER(oid_t)),
            len(sysUpTimeOID),
            ASN_TIMETICKS,
            ctypes.cast(
                ctypes.byref(uptime),
                ctypes.c_char_p),
            ctypes.sizeof(uptime),
        )

        # agent trap
        axl.snmp_varlist_add_variable(
            ctypes.byref(TrapVars),
            ctypes.cast(
                ctypes.byref(snmpTrapOID),
                ctypes.POINTER(oid_t)),
            len(snmpTrapOID),
            ASN_OBJECT_ID,
            ctypes.cast(
                ctypes.byref(TrapOID),
                ctypes.c_char_p),
            len(TrapOID) *
            ctypes.sizeof(oid_t),
        )

        # add variable
        for ArgOID, ArgData in args:
            ArgOID = ReadOID(
                self.AXData.NormOID(ArgOID)
            )

            ArgDataLen = 0
            ObjType = None
            if isinstance(ArgData, str):
                ObjType = ASN_OCTET_STR
                ArgDataLen = len(ArgData)
                ArgData = ctypes.c_char_p(ArgData)
            elif isinstance(ArgData, int):
                ObjType = ASN_INTEGER
                ArgData = ctypes.c_int(ArgData)
                ArgDataLen = ctypes.sizeof(ArgData)
                ArgData = ctypes.cast(ctypes.byref(ArgData), ctypes.c_char_p)
            elif isinstance(ArgData, float):
                ObjType = ASN_APP_FLOAT
                ArgData = ctypes.c_float(ArgData)
                ArgDataLen = ctypes.sizeof(ArgData)
                ArgData = ctypes.cast(ctypes.byref(ArgData), ctypes.c_char_p)

            # add variable
            axl.snmp_varlist_add_variable(
                ctypes.byref(TrapVars),
                ctypes.cast(ctypes.byref(ArgOID),
                            ctypes.POINTER(oid_t)), len(ArgOID),
                ObjType,
                ctypes.cast(ArgData, ctypes.c_char_p), ArgDataLen,
            )

        # send trap
        axl.send_v2trap(TrapVars)
        axl.snmp_free_varbind(TrapVars)